One aspect of the invention is directed to sunscreen formulations that protect the skin against the damaging effects of sunlight while providing the health benefits of increased vitamin D production by the body is disclosed. Another aspect is directed to methods for applying sunscreens.
One example embodiment of the current invention is a sunscreen formulation with active ingredients that screen as much of the damaging, cancer-causing ultraviolet radiation as possible while at the same time permitting passage of light in the wavelengths used by the body to synthesize vitamin D and for tanning.
Sunscreens are widely known and used to prevent the harmful affects of sun exposure. Each different active ingredient used in sunscreens has a unique profile in regard to which wavelengths of ultraviolet (UV) radiation it can absorb and what percentage of those wavelengths it can absorb. Traditionally sunscreen formulators, in their zeal to protect people who are exposed to sunlight from skin cancer and wrinkles, have combine complimentary active ingredients to filter UV radiation in a spectral overlap that screens the broadest spectrum of radiation possible. This broad spectrum approach, unfortunately, also blocks the beneficial wavelengths of radiation in approximately the 295 to 315 nanometer range which are needed for vitamin D synthesis in the skin.
There is broad agreement by vitamin D researchers that getting quantities of vitamin D that are sufficient for optimum health from diet alone is difficult, that vitamin D is produced in sufficient quantities when a sensible amount of sunlight at lower latitudes penetrates the skin and that a large percentage of the population would benefit from higher levels of vitamin D.
Vitamin D plays an essential role in the prevention of bone problems (of which one in twelve people living in higher latitudes is at risk), prevention of some sixteen common cancers (which together are responsible for 30 times more deaths than skin cancer) and modulation of neuromuscular and immune function. Research also indicates that sufficient levels of vitamin D may prevent or reduce the incidence of inflammation, multiple sclerosis, rheumatoid arthritis, hypertension, lupus, cardiovascular disease, type 1 diabetes and type 2 diabetes. Obesity is associated with lower circulating vitamin D levels.
Disclosed are significant, untapped health benefits and considerable commercial potential by the current invention.
Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to others, available as a dietary supplement and produced when ultraviolet (UV) rays from sunlight (or tanning beds) enter the skin. Essentially all terrestrial vertebrates, including humans, obtain most of their vitamin D requirement from casual exposure to sunlight. Application of a sunscreen, increased skin pigmentation, aging, hair and clothing all reduce vitamin D production in the skin.
Vitamin D is made in the body when a derivative of cholesterol called 7-dehydrocholesterol is converted to pre-vitamin D3 using the energy from radiation that has entered the skin. Pre-vitamin D3 then spontaneously changes itself into its isomer, vitamin D3. Vitamin D3 is then changed to 25-hydoxyvitamin D3 which circulates in the blood serum or is stored in the liver until needed. 25-hydroxyvitamin D3 is later changed in the kidneys or elsewhere into 1,25-dihydroxyvitamin D3, the main biologically active form.
Following are synonyms: pre-vitamin D3 is cholecalciferol; 25-hydoxyvitamin D3 is 25(OH)D3 or calcidiol; 1,25-dihydroxyvitamin D3 is 1,25(OH)2D3 or calcitriol. in this patent vitamin D stands for vitamin D3, and is sometimes used in a general sense.
The amount of sunscreen (or sunblock) applied to the skin can influence how much of the incoming UV radiation is absorbed, with a thicker layer generally absorbing more radiation. The current invention eliminates certain active ingredients which are known to be sticky or oily, especially in higher concentrations. One advantage of the current invention over traditional sunscreen concoctions is, surprisingly, overall better skin protection because the behavior of sunscreen users is such that they tend to use larger quantities and tend to re-apply more frequently when the ingredients are not as sticky or oily.
The action spectrum of epidermal vitamin D photosynthesis can be graphed in an absorbance curve showing that the peak absorbance for vitamin D synthesis is at about 297 nm, with large amounts produced between 295 and 305 nm, and lesser amounts produced farther from the peak of the curve between 290 and 295 nm and between 305 and 315 nm. (Wavelengths between 270 and 290 nm will cause vitamin D synthesis, but are for the most part filtered by the atmosphere, and therefore generally do not reach the body.) As the wavelengths increase from 290 to 315 nm, so does the relative intensity of UVB radiation reaching the earth's surface. Therefore as a practical matter, it has been discovered that although the absorbance by vitamin D precursors is highest in the 295 to 300 nm range, there is at the surface of the earth a higher intensity of UVB radiation available to the skin between 300 and 305 nm than is available between 295 to 300 nm
An important consideration of the current invention is that although the range of radiation that is filtered by the current invention's appropriate UV filter(s) may overlap part of all of the absorption range needed for vitamin D production (i.e. approximately 295 to 315 nm), the active ingredient(s) of the current invention permit the passage of sufficient quantity and quality of radiation for the body to effectively produce vitamin D. The current invention discloses a surprising improvement in sunscreen formulation that teaches away from mainstream full-spectrum screening approach.
Organic molecules known as UV filters (i.e. the active ingredients in sunscreens) have multiple atoms which can vibrate and rotate in relation to each other. Many closely spaced energy transitions mean that instead of absorbing exact frequencies of radiation, molecules absorb groups of frequencies of radiation. The many closely spaced absorption lines combine to make an absorption band. Sunscreens made from organic molecules absorb different percentages of the radiation. These percentages of absorption can be graphed as an absorption curve, with a range (i.e. the shortest to longest wavelengths absorbed) and the peak absorption (i.e. the wavelength which is most highly absorbed). The absorption range and the peak absorption vary by organic molecule. Different organic molecules have differences in how quickly their absorption drops off (“fat” curves as compared to “skinny” curves).
It is important to realize that even within an organic molecule's absorption range, it does not absorb evenly and absorptions near the ends of the range are usually low. Sunscreen manufacturers typically use several active ingredients for screening different parts of the UV spectrum, thereby providing protection from a broad spectrum of radiation.
Factors can influence the determination of the absorbance maximum and other spectral curve data, both for UV filters and vitamin D production, and it should be understood that the overriding essence of the present invention is to permit vitamin D synthesis by the body while blocking out other harmful wavelengths of radiation. For example, 4-aminobenzoic acid (PABA) has a maximum absorbance between 300 and 305 nm in its crystalline form, 289 nm when dissolved in alcohol, and 278 nm when dissolved in water. Therefore, formulations presented in the current invention which include or exclude UV filters based all or in part on the UV filter's absorbance maximum or other spectral curve data are not definitive and are subject to change.
The color of human skin is principally determined by two factors: constitutive pigmentation (which is the genetically-determined color of the skin) and facultative pigmentation (which is an acquired tan). About 72 hours after the skin has been exposed to UVB radiation in approximately the 295 to 315 nm range, a long-lasting base tan (facultative pigmentation) is most noticeable. This delayed tanning is an increase in melanin, through a process called melanogenesis. This invention is a sunscreen that permits the passage of a substantial portion of UVB light in the 295 to 315 nanometer range, thereby permitting the acquisition of a long-lasting base tan while blocking other harmful wavelengths. The sunscreen formulations of the current invention are surprisingly different from all other sunscreens in that those sunscreens filter a broad-spectrum of light, thereby blocking one's ability to get a long-lasting base tan.
Human exposure to UVA radiation has been associated with melanoma, premature aging, sagging, wrinkling skin, sun spots, tanning and immunologic effects. Formulations of the current invention provide substantial screening across the UVA range.